The present invention concerns compound structures and, more specifically, a set of adhesion projections between a poured component and a thin sheet of the compound structure. It is well-known, of course, that in compound structures their strength and other characteristics are decisively determined according to the adhesion which exists between the thin sheet component and poured component of the compound structure.
In the foregoing we have spoken of a thin sheet component, and this is understood to mean a steel sheet, plastic sheet or another equivalent thin sheet from the material of which the set of adhesion projections is produced by punching. The poured component of the compound structure is meant to be concrete, plaster, light weight concrete such as "Siporex", foam-expanded plastic, "Styrox", or another equivalent substance which may be brought into such condition that it will surround the set of adhesion projections constituting the object of the invention, in view of producing the intended compound structure.
The description of the invention now following is mainly concentrated on the embodiment of the invention wherein the poured component of the compound structure is concrete and the thin sheet is a steel sheet, which preferably furthermore serves as mold board in the pouring process and which need not be removed. It should be emphasized in spite of this that the invention is in no way confined to compound structures of concrete and steel; in contrast, all above-mentioned components of a compound structure may be mutually combined and in many such compound structures those advantages and aims are achieved which the invention is meant to gain. It is also possible to use two or more different poured components on opposite sides of the thin sheet, in which case the set of adhesion projections or tongues of the invention must be provided on both sides of the thin sheet.
The set of adhesion projections of the present invention is particularly appropriate for a compound structure used in concrete construction and which comprises, for instance, a thin sheet serving as a mold and a set of adhesion projections produced from the sheet material itself, a kind of "nails" by the aid of which one achieves, for instance, between the thin sheet used in making the mold and the cured concrete, an adhesion of such efficiency that the mold becomes a functional part of the structure and which in the case of a thin sheet of steel constitutes a steel reinforcement.
In the prior art it is commonly known to use thin steel sheet as the mold in the making of reinforced concrete slabs, columns and beams and in the making of relief cavities, but the task of the mold has generally been considered terminated after concreting is completed. In most instances the mold is dismantled after the concrete has hardened.
Furthermore, in the prior art corrugated sheets made of thin steel sheet are known, which are used in concrete construction both as mold and for reinforcement, the adhesion between the concrete and the thin sheet being accomplished by appropriate shaping of the sheet and/or by making on the surface of the sheet, knobs, grooves or folds. The drawback of these designs is the low adhesion between the concrete and the corrugated sheet, also the fact that this kind of mold is effective only as active reinforcement in a so-called unidirectionally bearing slab, so that this type of mold is unfit for use as reinforcement of, for instance, beams, columns and walls.
Perhaps the closest prior art is that disclosed in the German DOS No. 2 325,281, which teaches various sets of adhesion projections between concrete and thin sheet, said projections consisting of loop-like strips pressed outwardly from the plane of the thin sheet. FIGS. 7 and 8 of said reference display also adhesion projections which start substantially at right angles to the plane of the sheet on both sides of the punched aperture, or the respective projections are annular punch-outs. However, loop-like projections have the drawback that the concrete does not completely penetrate and surround the loop, whereby the adhesion between concrete and sheet remains poor. Furthermore, German DOS No. 2 325 281 contains no description of the significance which the shape and dimensional proportions of the adhesion projections and the size of the punch-out carry in view of the adhesion phenomenon.